This invention generally relates to bullets and more particularly to a small caliber projectile having a hollow point and a full metal jacket.
Jacketed bullets are well known in the art. The bullet typically is made of a lead alloy and has a jacket typically made of a copper alloy and covers at least part of the ogive and the cylindrical body portions of the bullet. This type of jacketed bullet gives a more controlled expansion in soft body tissue than an unjacketed lead bullet. Further expansion can be obtained upon initial target penetration by providing a hollow in the front end of the bullet. The front end may also be formed with cuts and/or ribs in the jacket or with cuts or ribs in the core within the hollow tip to further control the expansion upon upset of the bullet is soft tissue.
One typical hollow point jacketed bullet is disclosed in U.S. Pat. No. 3,157,137, assigned to the assignee of the present invention. This patent discloses a jacketed bullet with a rosette type of hollow point formed entirely from the open jacket end. Another is U.S. Pat. No. 3,349,711 which has external cuts in the ogive portion of the full metal jacket around the hollow tip. Another example is U.S. Pat. No. 4,550,662. In this patent, the hollow tip is formed with axially extending ribs in the soft metal core.
Another hollow point jacketed bullet, using aluminum for the jacket, is disclosed in U.S. Pat. No. 4,610,061, assigned to the assignee of the present invention. In this patent, the jacket extends only part way into the hollow and partial cuts are made in the jacket at the rim of the hollow point.
All of these bullets provide relatively predictable curling back of the jacket upon upset of the bullet in soft tissue. The petals formed by the jacket segments peeling back curl beyond 180.degree., folding under the expanding head of the bullet, along the cylindrical portion thereof. Thus the cutting swath in soft tissue is generally determined by the outer diameter of the expanded head of the upset bullet.
Maximum expansion of the head is desirable to maximize hemorrhaging and tissue damage. This maximized expansion maximizes the lethality in game animals. However, if the head expands too much, the bullet will separate into segments which limits the penetration. Accordingly, to obtain significant depth of penetration, the mass of the bullet must remain behind the head.
When a particular projectile is designed for law enforcement use consideration must be given to penetration performance through various barrier layers such as fabric, glass, and sheet metal. These barriers cannot all be accounted for in a single projectile design. To achieve a desired penetration depth after passing through known barriers with a desired upset shape, hollow point bullets are not presently used.
A hollow point bullet is optimized to achieve a desired upset shape following penetration through generally soft material, typically simulated by water or gelatin. If there is a barrier in front of the soft body tissue, such as a layer of sheet metal or a piece of glass, a hollow point bullet will deform immediately thus changing the penetration in the body tissue. However, it would be desirable to have a bullet which would penetrate through known barriers and still upset and expand in a manner that maximizes tissue damage.